The distribution of cancer of the colon, particularly its infrequency in Japan, its increase among Japanese immigrants to the United States and the high rate of this disease among North Americans and most Western Europeans, strongly indicates that a dietary factor, mainly high fat and animal protein, is of etiological significance in the development of this disease. Preliminary studies in metabolic epidemiology have shown that the dietary composition and intestinal microflora play a significant role in the compositon of intraluminal compounds such as cholesterol metabolites and bile acids which can act as cocarcinogens for the colon. The overall objective of proposed research is to delineate the relationship among dietary components, intraluminal compounds, intestinal microflora and colon cancer in man, and to develop a biochemical and/or a bacterial indicator for colon cancer. In order to elucidate the etiological role of bacterially modified intraluminal compounds on the incidence of colon cancer , we will analyze feces of high risk and low risk populations, patients with colon cancer, polups, familial polyposis, ulcerative colitis and Crohn's Disease for cholesterol metabolites, bile acids, tryptophan metabolites, microflora and bacterial Beta-glucuronidase activity. From these studies, we wish to develop a biochemical and/or a bacterial indicator which distinguishes low and high risk populations for large bowel cancer.